Factors Affecting Photosynthesis

During the process of photosynthesis, there are certain factors that alter (speed it up or slow it down) the rate at which the process is carried out. Three major factors that will be discussed are light intensity, carbon dioxide concentration, and temperature.


Light Intensity (Sunlight)


The graph above shows how the rate of photosynthesis may be coupled with the available light (sunlight).


Effect of light intensity on the rate of photosynthesis

Photosynthesis is dependent on light from the sun; as the light intensity increases, the rate of photosynthesis increases at a similar rate. Overtime the rate of photosynthesis falls off and begins to level off as other factors become limiting, in other words, there is a point at which no further addition of light will benefit the plant and the rate of photosynthesis now becomes dependent on other factors. This is called light saturation and is usually reached at 10000 lux.


Carbon dioxide concentration

Carbon dioxide is needed to make sugars. Carbon dioxide concentration in the atmosphere is about 0.03% but an increase in the percentage of carbon dioxide available in the air will result in an increase in the rate of photosynthesis. There is also a point where any further increase in carbon dioxide concentration will not lead to an increase in the rate of photosynthesis.

To some extent both the day and night reactions of photosynthesis are enzyme controlled and therefore temperature sensitive. As with all enzyme controlled reactions there is an optimum temperature. The effect of temperature on enzyme controlled reactions is shown in the next section.

Other factors that may affect photosynthesis include:

-Chlorophyll concentration



-The stomata on leaves (whether they are open or closed)


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